1. Field of the Invention
This invention relates generally to machines used for separating particulate of various sizes into separate piles of particulate of like size, and more particularly to an improved mobile machine that has a plurality of vibrating screens and conveyors for accomplishing particulate separation.
2. Description of the Related Art
It is well known to pour mixed particulate matter onto a vibrating screen to separate the particulate into matter with dimensions greater than the openings in the screen and matter with dimensions less than the openings in the screen. The matter with dimensions less than the openings in the screen falls by gravity through the screen openings and is collected beneath the screen. Alternatively, the particulate matter that falls through the screen can be directed onto a conventional conveyor that conveys the particulate away from the screening part of the machine and discharges it on a pile or in a container.
Many machines having such screens and conveyors are designed to be portable and have various combinations of vibrating screens and conveyors. Many are able to be towed on the road by a large vehicle, such as a tractor-trailer type tractor. As such, these machines ordinarily have hitches, legs and wheels conventional for towed vehicles. Alternatively, such machines can be towed onto a trailer and hauled by trailer. However, this can be difficult if the machine is the same size as the trailer.
The benefits of being roadworthy are significant, and often are a limiting factor in the design of these machines. For example, virtually every machine is restricted in width, length and height to maximum dimensions that enable the machine to be hauled on the highway.
One conventional machine is shown in U.S. Pat. No. 5,234,564 to Smith, in which a plurality of conveyors convey particulate from a hopper to a screening apparatus, and then into separate piles. Although this machine has advantages over the prior art, it also has disadvantages.
Therefore, the need exists for a screening machine that overcomes the disadvantages of the prior art.
The invention is a portable machine for screening particulate. The preferred machine has an elongated frame, and the frame has a hopper end and an opposite, discharge end. A hopper is mounted to the hopper end of the frame and configured to receive particulate matter poured into the top of the hopper. A main conveyor is also mounted to the frame. The main conveyor has a receiving end beneath the hopper, and extends uphill toward a main conveyor rejecting end.
A screening device, preferably a vibrating screen driven by a rotary motor driving eccentric weights, has an upper screen and a lower screen. The screens have openings of different size, and the screening device is drivably mounted to the frame beneath the rejecting end of the main conveyor. The screening device extends from an upper end that is closer to the hopper end of the frame to a lower end that is closer to the discharge end of the frame. Thus, the screening device goes downhill away from the main conveyor.
An underscreen conveyor is mounted to the frame and is disposed beneath the screening device for catching particulate that passes through the screening device. The underscreen conveyor has an upper end near the upper end of the screening device and a lower end near the lower end of the screening device, and in a preferred embodiment the underscreen conveyor is substantially parallel to the screening device""s screens.
A first lateral conveyor is mounted to the frame with an inboard end near one of the ends of the underscreen conveyor. The first lateral conveyor extends laterally outward from the frame for conveying particulate that falls onto the underscreen conveyor laterally of the frame. A second lateral conveyor is mounted to the frame with an inboard end near the lower end of the screening device. The second lateral conveyor extends laterally outwardly of the frame for conveying particulate that fails to pass through the lower screen of the screening device laterally of the frame.
A chute is connected to the frame at the lower end of the screening device and extends downhill from it for directing material that fails to pass through the upper screen off of the machine. A pair of endless tracks is mounted to the frame substantially intermediate the frame""s length. The tracks are drivingly linked to a prime mover for driving the tracks, thereby moving the machine.
In a preferred embodiment the underscreen conveyor is only drivable in a downhill direction from the upper end to the lower end. Furthermore, the first lateral conveyor mounts near the lower end of the underscreen conveyor. This provides the advantage that the piles of material are both as close to the discharge end of the frame as possible, thereby permitting loading of the hopper from both sides without interference from the piles of particulate.